


Transplant

by Askellie



Series: Appleverse [2]
Category: Undertale (Video Game)
Genre: Collars, Consensual emotional control, Consentacles, Crosstale Sans (Undertale), Crosstale Sans/Dreamtale Nightmare Sans (Undertale), Crosstale Sans/Dreamtale Sans | Dream (Undertale), Dreamtale, Dreamtale Nightmare Sans/Dreamtale Sans | Dream (Undertale), Ecto-Genitalia (Undertale), Kinda pregnancy anyway, M/M, Obedience, Overstimulation, Ovi except with apples, Oviposition, Poor Crosstale Sans (Undertale), Pregnancy, Soul Sex, Tentacles, Underverse, X-tale
Language: English
Status: Completed
Published: 2020-09-05
Updated: 2020-09-05
Packaged: 2021-03-07 03:06:42
Rating: Explicit
Warnings: No Archive Warnings Apply
Chapters: 1
Words: 3,648
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/26299870
Author URL: https://archiveofourown.org/users/Askellie/pseuds/Askellie
Summary: Nightmare had given a full lecture on his research and expectations that Cross is pretty sure neither he nor Dream had wholly understood or listened to. The gist Cross had come away with was that this new method would allow him to give birth to the apples in a more traditional manner, producing several at a time instead of the single, painful one that he could gestate in his soul.A non-canon extension onSeeding. (Apple pregnancy, anyone?)
Relationships: Cream - Relationship, Crossmare, Dream/Cross, Dreammare, Nightmare/Cross, Nightmare/Dream, Nightmare/Dream/Cross, Sans/Sans (Undertale)
Series: Appleverse [2]
Series URL: https://archiveofourown.org/series/1910914
Comments: 20
Kudos: 291





	Transplant

**Author's Note:**

> I ran a poll on my twitter to see which shameless kink I should write: collars, tentacles, eggs or obedience.
> 
> The overwhelming response was 'all' of them. So that is what you get.
> 
> This is set in the same vein as my fic '[Seeding](https://archiveofourown.org/works/25783966)' but isn't necessarily canon to it. I'm more attached to the idea of Cross having to painfully force the apples out one-by-one, so this is more of a 'what if' idea that exists because I am extremely thirsty and so many people loved the idea of concubine Cross getting happily egged by his twin owners.

The visceral reaction Cross experiences when Dream presents the collar is more intense than he expects. His soul goes hot and tight, pulsing with a beat he’s suddenly achingly aware. The gleaming circlet of gold is far different from the rough, utilitarian collars they use in Fell-verses. This one is elegant and smooth, the hinge made to blend in seamlessly with the rest of its shape. It looks like a smaller version of Dream’s coronet, and that added emphasis of ownership makes Cross flush in a way that gets Dream giggling.

“You like it.” Dream sounds inordinately pleased. 

Cross can only nod mutely. He's worn Dream’s emblem openly for years, though never fully shedding the distinctive X symbols of his original universe’s royal guard. Though he's never raised a complaint, he’s missed having those markers on his person ever since Nightmare took responsibility for his wardrobe. They’re not necessary embellishments, but Cross enjoys them for reasons he can’t quite articulate. It’s why the sight of the collar fills him with an almost dizzying surge of want, hands shaking softly at his sides.

There’s a sudden speculative gleam in Nightmare's eyelights that Cross tries to pretend he doesn’t notice.

Meanwhile, Dream is happily explaining, “I hoped it wasn’t too simple since we had to have it made in a hurry. I’ll get an even better one for you later.”

Cross is never more aware of their twinship than when Dream and Nightmare are eyeing him with those identical looks that say they fully understand the thoughts Cross would never dare to speak out loud. His immediate spluttering protest is smoothly overridden by Nightmare who mildly suggests, “Why don’t you put it on him?”

Dream lights up with pleasure, reverently lifting to the collar to Cross’s neck. Cross swallows thickly to try and banish the unseemly flood of saliva welling up on his tongue. His spine is straight, posture unwavering as Dream carefully snaps the band around his throat. The moment it closes, Cross feels a giddy high of overwhelming positivity. It’s like hugging Dream on a warm spring day in the middle of a celebrating pacifist AU -- a rare alignment of all things good and wonderful. The flush of unbridled delight instantly makes him smile, almost compelling him to break out in inexplicable giggles. He resists, but only barely. Instead, the sound that escapes from him is a shy purr that thrums deep and contentedly in his chest.

“Oh!” Dream seems delighted. “You don’t do that very often. It’s working, then?”

Cross nods as his bones quiver pleasantly with the resonance inside his ribcage. He feels so _good_. He wants to wrap Dream up in his arms and get lost in that joy. He wants to be touched, and kissed and praised by that sweet, familiar voice. He wants-

Blinking with slow, indulgent languor, Cross finds himself looking over at Nightmare. An unexpected barrage of thoughts crossing his mind. Nightmare notices and balks, looking uncharacteristically flustered. It’s...adorable? “What?”

Cross’s purr inadvertently kicks up a notch, but he doesn’t know how to put what he wants into words. Instead he looks at Dream, plaintive and eager.

“Yes, don’t worry. We’re going to take such good care of you,” Dream croons. He understands, of course he does. Cross believes him instantly, nearly swooning a daze of trust and love and gratitude. Dream steadies him, gently murmuring, “Can you summon your soul for me?”

Dream smells like sunshine and fresh grass even though there’s little of either left in Dreamtale. Not even years of Nightmare’s efforts have restored the AU to its former glory. It's possible that the real balance can only be fixed by Dream himself.

Cross leans into him, taking a deep breath, and summons not only his soul but the full shape of his ectobody from the bottom of his ribs all the way down to his knees. Despite his eagerness, his concentration isn’t very precise in his current haze of euphoria. He can only hope that his practiced efforts will ensure that all the necessary parts are there. He reaches down absently to check, his fingers curling down between his legs to feel the new shape of his pussy. A fleeting tingle of shame tries to take hold, but it’s completely eclipsed by the much more prominent excitement amplified by the collar, knowing that Dream and Nightmare are watching him openly.

“You put a lot of intent into that thing, didn’t you?” Nightmare muses. His efforts to sound nonchalantly unaffected don’t quite hit the mark. There’s raw interest in his gaze as he shuffles closer, eyes fixed on the slick spreading out over Cross’s probing phalanges. He thinks the parts are the right shape. The outer lips are soft and pliable, the inner slit feels hot and is already starting to feel slippery as his fingers quest further. Cross carefully dips a finger into his own entrance, making a soft sound of surprised enjoyment. It’s not that he’s never used his pussy before, but right now it feels so much better than he’s used to.

Both twins are staring at him. Dream has to swallow a few times before he can respond. 

“I wanted to be sure it was enough.” Dream takes Cross’s soul from where it’s hovering beside its owner’s sternum, stroking it gently. It pulses happily in his hand, obediently growing more wet as repeated encouragement has trained it to do. “Do you think it’s okay?”

“We’ll just have to keep it balanced,” Nightmare says firmly, his tentacles curling out from behind him, reaching for Cross. There’s a feral growl in his voice when he says, “Come here.”

Cross is a very willing victim, allowing himself to be captured and dragged unceremoniously into Nightmare’s lap. His back rests against Nightmare’s chest, thighs splayed wide and open in offering. His breath hitches in a shaky moan as Nightmare reaches down between his legs, phalanges folding over Cross’s in a surprisingly affectionate entwinement that quickly turns to an indecently shared exploration of the lips of Cross’s pussy. Two tentacles hook beneath his knees, ensuring Cross can’t close them as a third insinuates itself among the tangle of their joined fingers. It undulates through the slickness of his growing arousal before easing its way inside him. Cross’s skull falls back against Nightmare’s shoulder, his voice breaking on an unsteady cry of encouragement.

Theoretically, this should be easier than forcing the apples out of his soul. If Cross still had the capacity for nervousness, he would be, but Dream’s collar is a safety net of positivity; a swaddling of reassurance and a lens to heighten the pleasure. Those are merely beneficial side effects of its true purpose; keeping his soul in balance. He needs a strong positive influence to counter the innate negativity of Nightmare’s apples until Dream’s touch can purify them, especially since this time he’s going to be carrying more than one.

His soul is too small for such a feat, of course, but Nightmare thinks they can make use of the rest of his body to help expedite the process. Even if his ectobody isn’t as concentrated with the raw magic the apples need to grow, there’s apparently lots of useful intent and significant in the formation of a womb that allows it to make a suitable alternative vessel for the fruits. Nightmare had given a full lecture on his research and expectations that he’s pretty sure neither he nor Dream had wholly understood or listened to. The gist Cross had come away with was that this new method would allow him to give birth to the apples in a more traditional manner, producing several at a time instead of the single, painful one that he could gestate in his soul.

It was also a method that required Nightmare to fuck him in the much more traditional manner, an idea Cross had been careful not to think too hard on until the liberating bliss of the collar allowed him to do so without guilt or conflict.

When they first started creating the apples, Nightmare was careful to touch Cross no more than was needed; remaining as respectful and distant of boundaries as was possible given the implicit intimacy of the act. Now, all restraint has been discarded. Nightmare has a firm arm wrapped around Cross’s waist as his tentacles work enthusiastically over his body, stroking Cross into a fervor of whimpering moans. Cross’s light robe hangs askew, the sheer material seeming to melt off him like spun sugar as it’s drenched with the sweat of their exertion. Even the regularity of his nudity hasn’t fully erased his embarrassment, but the added shame somehow feels good. He can’t tell if that’s the collar’s influence or just his own innate perversion, but he doesn’t want to overthink it. He just wants to clench down on Nightmare’s tentacle and let it push him over the fast approaching edge of climax rising up in his sweltering bones.

“You’re so loud today,” Nightmare murmurs gently against Cross’s flushed cheek. His fingers slide unerringly towards Cross’s clit and pinch the nub of sensitive nerves with approval. His order is an unquestionable demand. “Come for me.”

 _For him_. Those words are all Cross needs, and he obeys, his voice rising to a wail as he rocks senselessly between Nightmare’s hand and the tentacle still thrusting into him. It goes deeper with each thrust in a way that might verge on painful if the tingling aftershocks of orgasm weren’t still rippling through him, leaving him in a tingling, anaesthetised daze of satisfaction. Nightmare gives him a moment to recover, possibly probing Cross’s emotions because his next words are full of infallible confidence. 

“He’s ready.” The tentacle in his pussy pulls out for a moment, leaving Cross disappointedly empty. Cross whines, feeling an ache as his inner walls clamp down on nothing. Nightmare’s hold tightens to limit his dissatisfied squirming. “Put it in, Dream.

Cross’s soul is dripping wet, Dream’s saliva adding a helpful coat to Cross’s natural slickness. He kneels down between Cross’s legs, beaming reassuringly before working his fingers into Cross’s entrance. Cross’s eyes go wide, not just at the aggressive stretch of multiple fingers prying him open, but from the indescribable feeling of his soul being pushed into his cunt. Even with the prior stretching, his passage is still narrow enough that he feels constricted from all sides, tightly encased, and for a moment he can’t perceive anything else. It’s verging on too much ( _too good_ ) until he’s pulled back to his senses by the grounding squeeze of Nightmare’s tentacles on his shoulders.

“Breathe.”

The command helps. Cross gasps sharply, focusing on the simple acts of inhalation and exhalation, and the pressure gets more bearable even though Dream is still pushing his soul in deeper. His hands are small and delicate, but as all four fingers and then the bridge of his knuckles push into Cross it feels impossible to get enough air. He can’t catch his breath, feeling light-headed and fragile. It takes him a moment to realise Nightmare is speaking to him, and even longer to catch the gently coached words being murmured into his acoustic meatus. 

“You’re doing so well. Just relax. It’s going to feel so good.” Nightmare tugs on the collar at Cross’s throat even though its positivity must sting him, but the little jolt is a pleasant distraction, helping Cross focus as Nightmare fervently whispers, “ _I’m_ going to make you feel so good. I’m going to fill you up until you can’t move or think, and we’re going to take such good care of you.”

Dream’s entire hand is lodged inside him, applying steady pressure on his soul as it seems to hit some barrier that tries to force it back. Nightmare’s hands are stroking him, one on his belly and the other on his clit, his touch full of promise and the sweetness of the words he’s whispering into Cross’s ear. Cross’s trembling body lurches, and the obstruction inside him seems to give way, letting Dream shove his soul in deeper than Cross would have thought possible. It burns briefly, the stretch is so unusual and tender as both his soul and his body fighting for space before somehow resolving in a dissolution of tension that makes him come again, his body wracked with desperate relief as he gives an unrestrained wail.

It leaves him reeling, senses swimming in a glossy stupor of incoherent bliss. For a moment he can’t feel anything but the purr in his chest, a steady hum beneath his sternum and in the back of his throat. Only belatedly does he become aware of Dream holding his face, trying to encourage Cross’s eyes to focus. 

“Cross?” he calls softly, his voice like the beacon of a lighthouse. Cross turns unerringly towards him, blinking with muzzy delight. Dream grins back at him. “Are you still okay?”

Cross gives a drunken nod that makes Dream pout and poke his nasal ridge reprovingly. “With words, Cross. Tell me you’re okay.”

“I’m okay,” Cross parrots obediently, his voice warbling with the intensity of his purr. At Dream’s fondly exasperated expression, Cross forces himself to add, “I’m good. Really good. I like it.”

Everything is soft-edged and wonderful. Cross feels like he could stay this way forever, but suddenly the world tips around him and he finds himself on his back amidst the nest of cushions on the floor. Nightmare is above him, his mouth twisted in a leer that once would have made Cross break out in a cold sweat. Now it makes him feel hot, like his bones have been dipped in gasoline, ready to be set alight.

“Do you want to continue, then?” Nightmare asks, though he’s clearly not asking because he needs to; only because he wants to hear Cross say it. Normally Cross would resist, would bare his teeth and at least force Nightmare to work for it, but right now what he wants even more desperately is for Nightmare to make good on all those darkly whispered promises. 

Cross wraps his arms around Nightmare’s neck, holding him in place like the guardian might try to escape. With unabashed honesty, he begs, “Please.”

Nightmare’s bewildered blink is immensely gratifying, as is the way he curses under his breath as he scrambles to shed his clothing with haste. His own urgency and Cross’s clinging grip make the process slower and clumsier than it needs to be. Nightmare’s innate elegance and care are noticeably absent, overridden by an almost animalistic hunger as he lines himself up with Cross’s eagerly clenching passage and with one forceful motion thrusts fully into him.

“Fuck!” Cross yelps, the obscenity slipping out of him. Normally he tries not to curse in Dream’s hearing, but even after being thoroughly stretched, taking Nightmare’s cock feels unspeakably intense. 

“Fuck,” Nightmare agrees, his own voice tight. He’s buried in Cross’s body to the hilt, both of them clinging fiercely to each other. Cross has barely adjusted to the feeling of fullness before Nightmare finally starts to move, hips dragging back just slightly before snapping forward like he can’t bear to pull himself out of Cross’s body, and Cross can feel the impact all the way up to where his soul is housed inside his womb. His gurgle of shock seems to spur Nightmare into action, and suddenly Cross finds himself being fucked ruthlessly and roughly into the floor, driven almost senseless with each thrust.

Nightmare isn’t any bigger than Dream, their bodies identical aside from the coating of slime, but the added weight of Nightmare’s tentacles makes him heavier. Cross feels both pinned down but protected and safe. There’s a faint burn in his sockets that he tries to blink back, fumbling blindly against the cushions until Dream’s hand finds its way into his own. He also has a finger hooked into the collar, applying a steady pressure, likely preparing to adjust its level of positivity as needed.

It doesn’t take long for Nightmare to come into him the first time, filling Cross with a flush of heat and a teetering dip in his emotions that he can feel Dream working to correct. He can feel the negative essence surrounding his soul as it penetrates his womb, but it’s not as strong as having it fully inside the construct like he’s used to.

Tears end up spilling over Cross’s sockets, but he can’t even discern if the feeling behind them is a positive or a negative one. Either way, the sight of them seems to spur Nightmare on, and with a low snarl he bucks into Cross with renewed effort. He must be using magic to manipulate himself into staying hard, not allowing himself a break before chasing the next climax.

“You’re doing great, Night,” Dream encourages, keeping his aura tightly reined so only Cross can feel it, ensuring he won’t disrupt his brother’s efforts. If the end result of this method is meant to be easier on Cross, it’s also much harder on Nightmare, who has to force the essence of the apples out in much faster succession than he’s used to. It’s an effort that’s clearly taking its toll, parts of his body seeming to melt away before shakily reforming, shades of purple and cyan seeping out to blend with the black as Nightmare grunts and hisses and forces himself to reach his peak.

He rises to climax again, and again, until Cross’s passage aches from the friction and his insides feel bloated and tight. His cunt feels like a ruin, fluids squelching obscenely each time Nightmare fucks into him, the excess dripping down to stain the pillows and the floor in a disaster that some poor soul -- possibly Killer -- will have to clean up later. The pressure in his stomach is starting to feel uncomfortable, but Cross keeps his arms around Nightmare’s shoulders, murmuring an inarticulate echo of the reassurances Nightmare gave him earlier. He’s so drunk on exhaustion and emotional whiplash that he’s pretty sure the words coming out of his mouth are utterly senseless, but it’s the tone that counts and it seems to help Nightmare reach one final release with a harsh, strangled cry before he collapses on top of Cross in a shapeless pile of quivering ooze and tentacles. 

Cross feels just as drained, but Nightmare’s rare display of vulnerability makes him feel a twist of emotion he was pretty sure had only ever belonged to Dream. Numbed with fatigue, he doesn’t fight the impulse to nuzzle against Nightmare’s temple, purring fiercely in a wordless expression of comfort.

After a few moments of enduring Cross’s besotted affection Nightmare chuckles tiredly and pulls back. Whatever unguarded emotions slip through to show on his face pass too quickly for Cross to catch them, and Nightmare quickly turns his attention down to the noticeably swollen bump of Cross’s abdomen. Dream also shuffles forward, eager to see.

Beneath the purple sheen of Cross’s ectobody is a swarm of dark blotches around the pale light of his soul. As they watch, the inky essence starts to split and multiply, each surging out to claim its own space before starting to solidify as they draw on the ambient magic of their new enclosure. 

Cross winces slightly as the hardening spheres start to press against both the inside of his womb and the surface of his soul trapped in amongst them. The bloating pressure isn’t pleasant, straining painfully against his insides, but he trusts that the twins will keep him safe. He lies back against the sweat-drenched cushions and tries to relax as the apples continue expanding. They’re not growing as fast as the ones planted in his soul usually do, but the sheer number of them is faintly concerning.

“H-how many?” he manages to ask, breath wheezing unevenly as he feels his insides shifting unnaturally to accommodate the swelling brood. Thankfully he doesn’t have any real organs to displace; technically his womb could grow to fill the entirety of his abdominal cavity, although it’s not a very comfortable sensation.

Nightmare leans in and starts counting, having to grope and press around Cross’s abdomen to try and discern how many distinct apples have started to take form. “Seems like...twenty.”

Cross’s emotions are back in balance enough for him to feel sincerely aghast. The whole idea was to speed up the process of reconstructing the apples, but he had expected maybe five or six at a time. Not this. “ _Twenty_?”

“Blame my brother,” Nightmare tells him frankly. “I had to balance out all the intent he put in that collar. He overdid it.”

“Oops,” Dream says, sounding abashed, but also amused. Nightmare slants an irritated look at him, but there’s a hint of contrition there too. Maybe they both overdid it. 

Cross looks down at his rounded stomach. He can still feel the apples growing, pulsing, shifting around. There’s a lot of pressure around his soul, like the fruits are jostling for space to be close to it. “How long until they’re ready to come out?”

Nightmare narrows his eyes in silent calculation. “Might be a day or two. Make sure you eat a lot and regularly. They’ll be taking a lot of energy from you.”

Cross sighs. Even if they’re only apples, having them inside him as well as the fullness of his body summoned makes him feel heavy and useless. There’s already an ache in his lower spine that makes him long for a hot bath and maybe a massage. “Yes, Boss.”

The old title slips out of him, unintentional and unnoticed. Nightmare gives him an odd look, but Dream seems strangely pleased.

“You should rest,” he says, squeezing Cross’s hand. “Let me and Nighty take care of you.”

Cross nods tiredly and lets his sockets drift shut, oblivious to the silent, meaningful looks the twins exchange over his head.


End file.
